The present invention relates to a pulley assembly for a continuously variable transmission. Concretely, it relates to the secondary-side pulley device of a belt type continuously variable transmission for a motor vehicle, and more particularly to the clinch connection between the sideward flange portion of a movable pulley and the open end portion of a hydraulic cylinder.
As a continuously variable transmission of this type, there has been proposed one of a construction which has a primary pulley on an engine side and a secondary pulley on a wheel side, and in which a belt is wound over both the pulleys. A primary pressure for a speed change is supplied into and drained from the cylinder of the primary pulley, while a secondary pressure corresponding to a transmission torque is normally supplied into the cylinder of the secondary pulley. Herein, when an revolution speed of the secondary pulley is sharply raised by the variable speed, a centrifugal oil pressure takes place in an oil chamber of secondary pulley and the primary pressure balancing the secondary pressure fluctuates.
In the secondary pulley on the output side, therefore, a balance chamber is provided in adjacency to a secondary chamber so as to cancel the centrifugal oil pressure of the secondary pressure with the centrifugal oil pressure of the balance chamber. In this case, the secondary pulley side includes a partitioning plunger which is fixed integrally with a secondary shaft. The cylinder which is common to the secondary chamber and the balance chamber is snugly fitted on the plunger through an oil seal. Besides, the open end part of the cylinder on one side thereof is integrally connected to the movably pulley side of the secondary pulley.
Regarding the construction of the secondary pulley, there has heretofore been, for example, a prior art technique disclosed in the official gazette of Japanese Utility Model Registration Application Laid-open No. 52359/1987. Here, it is indicated that a hydraulic servo cylinder and a cover for canceling a centrifugal oil pressure are dividedly formed, that one end of the cylinder is fastened to a movable pulley side, that the oil seal is snugly fitted in a plunger of the cylinder, and that the cover is connected integrally with the outer end of the cylinder by the engaging a protrusion in a groove and the baking of a sealing rubber ring.
In the prior-art technique mentioned above, problems such as the complication of mounting and the increased number of man-hour are involved because the cover for canceling the centrifugal oil pressure is formed separately from the hydraulic servo cylinder.
In this regard, it is considered that the cylinder is integrally formed so as to serve also as the cover of the balance chamber and is snugly fitted on the oil seal of the plunger, whereupon the open end part of the cylinder is clinched and connected to the movable pulley side. With this construction, the connection is facilitated. Since, however, the chamfering of the open end part of the cylinder is limited in point of ensuring the clinch, the oil seal of the plunger is liable to undergo nibbles or defects in fitting the cylinder on this oil seal.
Accordingly, the clinch connection of the cylinder needs to be contrived so as to prevent the nibbles of the oil seal of the plunger attributed to the cylinder.